package bishi.aiqiyi;

import java.util.Scanner;

/**
 * @author: 唐小尊
 * @email: 1171702529@qq.com
 * @cate: 2021/08/01 15:23
 */
public class one {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        String str = sc.nextLine();
        str = str.trim();
        String[] strs = str.split(":");
        if (strs.length<2) return;
        String[] ints = strs[0].split(",");
        if (ints.length<1) return;
        int size = Integer.parseInt(strs[1]);
        int left = 0,right =0;
        int sum = 0;
        double res = 0;
        while (right<ints.length){
            if (right-left<size){
                sum+=Integer.parseInt(ints[right]);
                right++;
                continue;
            }
            int last = sum;
            sum+=Integer.parseInt(ints[right]);
            sum-=Integer.parseInt(ints[left]);
            right++;
            left++;
            res = Math.max(res,(double)(sum-last)/last);
        }
        System.out.println(String.format("%.2f",res *100));
    }
}
